The average mainline long-haul speed of a freight train is probably around 50mph. The average speeds of freight trains are remarkably lower since trains spend a lot more time stopping (if you're dealing with local freight, you're going to be stopping every few miles to detach or attach a few train cars). Looking at <http://www.railroadpm.org/Performance%20Reports/BNSF.aspx>, the intermodal trains (which tend to be between major shipment terminals and not including local businesses) are averaging at ~30mph.

Is that because the slow speed is efficient, or because it's cheaper to avoid improving the track to support higher speeds?

Freight trains in Europe are much faster[1] -- but that could be because they often need to fit in with the schedule of passenger trains using the same lines (which themselves require the track to be maintained to a high standard).

[1] Citation needed, I only have observations of them going at a decent pace through stations I'm waiting at.

The train networks in the US are more optimized for, and better at freight traffic, while Europe is more optimized for, and better at, passenger traffic

http://www.coyoteblog.com/coyote_blog/2008/02/european-vs-am...

That's probably exactly why freight trains are faster in Europe:

http://www.economist.com/node/16636101

One really nice anecdote from that response:

> In fact, the freight rail system is so efficient that to some extent we've obviated the need for the Panama Canal. Many Asian container ships bound for Europe actually make port in Seattle or Vancouver, offload their containers onto trains which shoot across the country to New York or another eastern port where they are reloaded on ships for the trip to Europe.

That is impressive.

Though I suspect soon enough the Northwest Passage will be clear for enough of the year that most freighters will just sail through the Arctic. Perhaps both Panama's government and North America's railroads should be pushing hard for a carbon tax.

Good question, I'm not sure how much speed plays a role in train efficiency. It's no doubt some of each of your alternatives, I imagine. Even the higher speed ones are more like 60-70MPH. Nobody seems to be the least bit interested in building a TGV freight version, for example, even to run on existing TGV lines.

[1] has rolling resistances for railways and cars on roads, which are almost an order of magnitude apart.

Intuitively, I'd expect that once the train has accelerated, it will keep its momentum very nicely, and (if electric) can easily return energy if it does need to slow down.

I can't find a real-world coasting distance for a train on level track, only reports during accidents/near misses -- 5km under emergency braking on a slight downhill slope, for one! [2]

[1] https://en.wikipedia.org/wiki/Rolling_resistance [2] https://www.gov.uk/government/uploads/system/uploads/attachm...

Rolling resistance is roughly constant with speed, so it's unimportant for efficiency. The main driver of changes of efficiency with speed is aerodynamic drag, because that increases with the square of the speed. Trains presumably have very low aerodynamic drag because they're long and thin.

The calculation is straight forward. The coefficient given for rolling resistance is 0.0004 for rail which means that .0004W is the frictional resistance of the track. Given a train going at velocity v then the train is accelerated by friction at a rate of -.0004W/m (F=ma so a=F/m) which is equal to -.0004g (W=mg).

Then to stop it will take t = v/.0004g which means that you will travel vt/2 in that time.

For example, if a train is cruising along at 30 mph (44 fps) then it takes 44 ft/s / .0004(32.2 ft/s^2) = 3416 seconds to stop which means that the train travels 14.2 miles under ideal conditions.

I suspect that the average speed of a moving train is higher than that, though. (In the same way that you can't take distance to the office divided by time to get there and conclude anything about average driving speed, due to time at stop lights, time in stop-and-go traffic, etc. When you're actually moving, you're moving faster than that statistic indicates.)